The above-mentioned waste products include, for example, industrial recycling products such as electronic scrap or slags from metal smelting, but also household waste of various compositions. The latter include primarily organic mixtures such as foodstuffs, plastics packaging, composite packaging, as well as inorganic components such as glass, metals and composites thereof.
These mixtures and composite elements pose problems in particular during disposal, since separation of the mixtures and of the materials contained in the composite has been carried out hitherto either not at all or only inadequately, with high consumption of energy. Most of these waste products are incinerated or dumped. Only waste products with low impurity content—for example cans of aluminium sheet—are subjected to material recovery treatment. More complex waste is not subjected to treatment or material recovery through lack of technical possibilities or the high cost resulting, for example, from wet-chemical processes or thermal processes.
In the conventional mechanical processing procedure, the composite element is broken up by way of the grain or particle size which is smaller than the respective layer thickness of the components. This breaking-up operation is generally effected by using an at least one-stage very fine crushing operation using suitable mills—for example, hammer, impact or counter-flow mills—possibly with the assistance of nitrogen for inerting and cooling purposes.
Known from FR-A-1 562 013 is a comminution mill comprising a rotor having a plurality of rotating discs and a cylindrical housing surrounding said rotor, in which material to be milled is fed by a worm device to the lower end of the rotor and is then picked up by the airflow of a fan disposed across the rotor above a sieve base and below the rotor bearing. The upwardly-impelled milling product is comminuted by so-called plaques de broyage, i.e. milling or crushing plates, which project radially from rotating rotor plates and are arranged close to the housing wall. The ends of the milling or crushing plates co-operating with the housing wall are in each case equipped with elliptical frames; these frames describe a constructed circle against the inner face of the housing and are claimed to assist the milling and comminution effect. Moreover, in the view of the author of FR-A-1 562 613, turbulences are additionally involved in this comminution process. A bypass which recirculates sieved-out coarse particles to the lower intake leads off from the housing of this comminution mill below the fan.
A comminution mill of this kind is also disclosed by DE-A-42 13 274, which machine is used as a micro-fluidised-separator mill for fine comminution of composite materials containing metals, in particular for recovering precious metals, from mounted circuit boards. The copper, for example, is reduced to a grain size of approximately 80 to 100 μm and removed via the separator air. Arranged at an opening of a bypass is a deflector edge which deflects the particles flowing at the periphery of the rotor into the bypass opening. The eddies produced by the rotary motion of the rotor are illustrated in the drawings in the manner of a comic strip phenomenon, without explanation of their significance in terms of process technology.
WO-A 9 305 883 contains a process flow diagram for recovering fibres from glassfibre-reinforced plastics or the like using a shredder, after which the shredded product is pulverised. Liberated fibres are separated from this powder and the remaining pulverised waste is used, for example, as filler. This process diagram contains a micro-mill referred to as a pulveriser which resembles that from FR-A-1 562 013 in construction.
In a process according to WO 95/25595 for treating composite elements of solid organic and/or inorganic composite materials such as composites of metal/metal, plastic/plastic, metal/plastic or mineral composites with metals and/or plastic materials, a mixture is fed to the flow-breakaway edges with an acceleration of 20 to 60 m/sec2 and a movement is established in the eddies which acceleratingly breaks up a mixture. In addition, during this separation or breaking-up procedure the adhesion between the components of the solid particles is overcome by acceleration and frictional forces which exceed the adhesion force, and the components of the solid particles are detached or removed from one another, the layers of the above-mentioned composite material being separated.
The known methods therefore have the object of processing, comminuting, homogenising and partially or wholly separating composite materials and mixtures of materials. Such methods are based in particular on mechanical shearing and crushing, on relatively uncontrolled fragmentation or separation in high-energy eddies.